SNO+

Mark Chen

Queen’s University

Neutrino Geophysics, Honolulu, Hawaii

December 15, 2005

1000 tonnes D2O

12 m diameter Acrylic Vessel

18 m diameter support structure; 9500 PMTs (~60% photocathode coverage)

1700 tonnes inner shielding H2O

5300 tonnes outer shielding H2O

Urylon liner radon seal

depth: 2092 m (~6010 m.w.e.) ~70 muons/day

Sudbury Neutrino Observatory

DepthMatters!

SNO Timeline

1998 1999 2000 2001 2002 2003 2004 2005 2006

commissioningPure D2O

Salt

Pure D2Oand desalination

3He Counters

NOW

added 2 ton of NaCl

• pure D2O phase discovers active solar neutrino flavors that are not e

• salt phase moves to precision determination of oscillation parameters; flux determination has no spectral constraint (thus can use it rigorously for more than just the null hypothesis test) – day/night and spectral shape are studied as well as the total active 8B solar neutrino flux

• NCDs installed and taking production data; final SNO configuration offers CC and NC event-by-event separation, for improved precision and cleaner spectral shape examination

?

• Fall 04 to Dec 06: SNO Phase III– 3He proportional counter array

• dedicated Neutral Current Detectors (NCDs)• taking production data

– data taking end date: 31 Dec 2006• will bring total uncertainty on 8B solar

NC signal below 5%– physics with heavy water will be

complete– heavy water will be returned

to AECL in 2007

what should be done next?

Beyond SNO

• SNO plus liquid scintillator → physics program– pep and CNO low energy solar neutrinos

• tests the neutrino-matter interaction, sensitive to new physics

– geo-neutrinos– 240 km baseline reactor oscillation confirmation– supernova neutrinos– double beta decay?

Fill with Liquid Scintillator

SNO+ Technical IssuesSNO+ Technical Issues

liquid scintillator selectionliquid scintillator selection compatibility with acrylic vesselcompatibility with acrylic vessel high light yield, long attenuation lengthhigh light yield, long attenuation length

reversing the acrylic vessel mechanicsreversing the acrylic vessel mechanics SNO: AV contains heavy water, must hold upSNO: AV contains heavy water, must hold up SNO+: AV contains scintillator, SNO+: AV contains scintillator, < 1 g/cm < 1 g/cm33, ,

must hold downmust hold down liquid scintillator purificationliquid scintillator purification

Acrylic Vessel Hold-down

• “rope net” being designed to hold down 15% density difference (buoyancy)

SNO SNO+

Scintillator Wish List

• high density (>0.85 g/cm3)• chemical compatibility with acrylic• high light yield, long attenuation and

scattering lengths

• high flash point• low toxicity• low cost

Linear Alkylbenzene

LAB Advantages

110

• compatible with acrylic (e.g. Bicron BC-531 is 95% LAB)– “BC-531 is particularly suited for intermediate sized detectors in

which the containers are fabricated with common plastic materials such as PVC and acrylics. The scintillator provides over twice the light output of mineral oil based liquids having similar plastic compatibility.”

• high flash point 130 °C• low toxicity (pseudocumene 2 4 0)

• cheap, (common feedstock for LAS detergent)• plant in Quebec makes 120 kton/year, producer

has been very accommodating• high purity

SNO+ Monte Carlo

• light yield simulations

KamLAND scintillator in SNO+

629 ± 25 pe/MeV

above no acrylic 711 ± 27 pe/MeV

KamLAND scintillator and 50 mg/L bisMSB

826 ± 24 pe/MeV

above no acrylic 878 ± 29 pe/MeV

KamLAND (20% PC in dodecane, 1.52 g/L PPO)

~300 pe/MeV for 22% photocathode coverage SNO+ has 54% PMT

coverage; acrylic vessel only diminishes light ouput by ~10%

LAB Scintillator Optimization

“safe” scintillators

LAB has 75% greater light yield than KamLAND scintillator

Light Attenuation Length

Petresa LABas received

attenuation length around ~20 m @ 420 nm

preliminary measurement

Default Scintillator Identified

• LAB has the smallest scattering of all scintillating solvents investigated

• LAB has the best acrylic compatibility of all solvents investigated

• density = 0.86 g/cm3 acceptable• …default is Petresa LAB with 4 g/L PPO,

wavelength shifter 10-50 mg/L bisMSB• because solvent is undiluted and SNO

photocathode coverage is high, expect light output (photoelectrons/MeV) ~3× KamLAND

Geo-NeutrinosGeo-Neutrinos

can we detect the antineutrinos produced can we detect the antineutrinos produced by natural radioactivity in the Earth?by natural radioactivity in the Earth?

Image by: Colin Rose, Dorling Kindersley

radioactive decay of heavy elements (uranium, thorium) produces antineutrinos

assay the entire Earth by looking at its “neutrino glow”

e

Geo-Neutrino SignalGeo-Neutrino Signalterrestrial antineutrino event rates:

• Borexino: 10 events per year (280 tons of C9H12) / 29 events reactor• KamLAND: 29 events per year (1000 tons CH2) / 480 events reactor• SNO+: 64 events per year (1000 tons CH2) / 87 events reactor

SNO+ geo-neutrinos and reactor background KamLAND geo-neutrino detection…July 28, 2005 in Nature

based on Rothschild, Chen, CalapriceGeophys. Res. Lett. 25, 1083 (1998)

geo- in SNO+

KamLAND

distance from detector [km]

frac

tion

of t

otal

flu

x

crust: bluemantle: blacktotal: red

SNO+ geo-neutrinosource integral

SNO+ Geo-neutrinos

a good follow-up to KamLAND’s first detectionpotential to really constrain the radiogenic heat flowpotential for geochemistry (separate measurement

of U and Th)simple geological configuration

old, stable, thick continental crust surrounds Sudbury smaller uncertainties?

Toy Example – Mantle Component

70-30: the 70 component has 10% uncertainty; that’s 7/30 = 0.23

80-20: the 80 component has 5% uncertainty; that’s 4/20 = 0.20

• leverage existing investment in SNO to get new physics for relatively low cost

• SNO+ is uniquely positioned to make several measurements (due to depth, geology, appropriate distance to reactors, low backgrounds)

• costs are:– liquid scintillator procurement– mechanics of new configuration, AV certification– fluid handling and safety systems– scintillator purification– electronics/DAQ spares or upgrades?

Extension of SNO Science

SNO+ in 2006

• SNO+ in Fall 2005 “proof of principle”– liquid scintillator identified– preliminary design to holddown the acrylic vessel

• need more collaborators• project management• scintillator purification R&D• electronics/DAQ plans…• full TDR by Fall 2006

– including process engineering and AV mechanics

• proposals to funding agencies by Fall 2006

SNO+ in 2007

• start of capital funding

• construction of hold-down net

• access detector after D2O removed

• scintillator procurement contracts

• …and on to converting SNO into an operating, multi-purpose, liquid scintillator detector with unique physics capabilities

p + p 2H + e+ + e p + e− + p 2H + e

2H + p 3He +

3He + 3He 4He + 2 p 3He + p 4He + e+ + e

3He + 4He 7Be +

7Be + e− 7Li + + e7Be + p 8B +

7Li + p + 8B 2 + e+ + e

p-p Solar Fusion Chain

Low Energy Solar Neutrinos

• complete our understanding of neutrinos from the Sun

pep, CNO, 7Be

CNO Cycle12C + p → 13N + 13N → 13C + e+ + e

13C + p → 14N + 14N + p → 15O + 15O → 15N + e+ + e

15N + p → 12C +

• best-fit oscillation parameters suggest MSW occurs

• but we have no direct evidence of MSW– day-night effect not observed– no spectral distortion for 8B ’s

• testing the vacuum-matter transition is sensitive to new physics

Neutrino-Matter Interaction

from Peña-Garay

vacuum-matter transition

plug in m2 = 8 × 10−5 eV2, = 34°Ne at the centre of the Sun →E is 1-2 MeV

• non-standard interactions

• MSW is linear in GF and limits from -scattering experiments g2 aren’t that restrictive

• mass-varying neutrinos

Friedland, Lunardini, Peña-Garay, hep-ph/0402266

Barger, Huber, Marfatia, hep-ph/0502196

pep solar neutrinos are at the “sweet spot” to test for new physics

New Physics25.0

NC non-standard Lagrangian

CHARM limit

Miranda, Tórtola, Valle, hep-ph/0406280solar density fluctuations:Guzzo, Reggiani, de Holanda, hep-ph/0302303see also Burgess et al., hep-ph/0310366 and also Balantekin and Yuksel, PRD 68, 013006 (2003)

pep

SNO CC/NC

m2 = 8.0 × 10−5 eV2

tan2 = 0.45

SSM pep flux:uncertainty ±1.5%

known source → precision test

Survival Probability Rise

sensitive to new physics:• non-standard interactions• solar density perturbations• mass-varying neutrinos• CPT violation• large 13

• sterile neutrino admixture

improves precision on 12

observing the rise confirms MSW and that we know what’s going on

stat + syst + SSM errors estimated

these plots from the KamLAND proposal muon rate in KamLAND: 26,000 d−1 compared with SNO: 70 d−1

11C Cosmogenic Background

3600 pep/year/kton >0.8 MeV

2300 CNO/year/kton >0.8 MeV

7Be solar neutrinos

using BS05(OP)and best-fit LMA

Event Rates (Oscillated)

resolution with 450 photoelectrons/MeV